Apparatus and methods for spreading fiber bundles for the continuous production of prepreg

Abstract

Apparatus for producing spread fiber bundles by strategic use of tension control throughout the device and use of higher differential speeds between driven rollers and line speed of the running fiber bundle are provided herein, along with methods for producing spread fibers, prepregs, and articles of manufacture therefrom.

The invention claimed is: 
     
       1. An apparatus for producing a spread fiber bundle comprising:
 a tension control module comprising:
 i) a tension building unit comprising a series of static bars configured to increase tension in a running fiber bundle moving in a traveling direction; and 
 ii) a tension reducing unit comprising a series of driven rollers configured to reduce tension in the running fiber bundle, each driven roller being independently rotatable, 
 
 wherein the tension reducing unit is positioned downstream from the tension building unit along the traveling direction of the running fiber bundle such that, during operation, the running fiber bundle makes direct wrapping contact with the surface of said static bars prior to making direct wrapping contact with said driven rollers, and wherein the peripheral surface speed of the driven rollers is at least three times the speed of the running fiber bundle. 
 
     
     
       2. An apparatus according to  claim 1  further comprising a spool of fiber for supplying the running fiber bundle, wherein the spool of fiber is positioned upstream from the tension building unit along the traveling direction of the running fiber bundle. 
     
     
       3. An apparatus according to  claim 1  further comprising a second tension control module in a different path than that of said tension control module, said second tension control module comprising a second tension building unit comprising a series of static bars, and a second tension reducing unit comprising a series of driven rollers, each driven roller of the second tension reducing unit being independently rotatable about its own axis,
 wherein the second tension reducing unit is positioned downstream from the second tension building unit along a traveling direction of a second running fiber bundle such that, during operation, the second fiber bundle makes direct wrapping contact with the surface of the static bars of said second tension building unit prior to making wrapping contact with the surface of the driven rollers of said second tension reducing unit. 
 
     
     
       4. An apparatus according to  claim 2 , wherein the final spread width of the running fiber bundle exiting the tension reducing unit is up to 3.5 times the original width of the fiber bundle. 
     
     
       5. An apparatus according to  claim 1 , wherein the tension building unit further comprising one or more low speed driven rollers operating at a slower speed than the speed of the running fiber bundle. 
     
     
       6. An apparatus according to  claim 1  further comprising a tension moderating section comprising a series of alternating driven rollers and static bars positioned between the tension building unit and the tension reducing unit along the traveling direction of the running fiber bundle. 
     
     
       7. An apparatus according to  claim 1  further comprising a separate drive motor for independently rotating each of the driven rollers such that the peripheral surface speed of the driven rollers ranges from 3 to 100 times the speed of the running fiber bundle. 
     
     
       8. An apparatus according to  claim 1 , wherein the static bars or the driven rollers contain a sanded surface finish. 
     
     
       9. An apparatus according to  claim 1  further comprising at least one rake. 
     
     
       10. An apparatus according to  claim 9 , wherein the rake is situated upstream from the tension building unit. 
     
     
       11. An apparatus according to  claim 9 , wherein the rake is situated between the tension building unit and the tension reducing unit. 
     
     
       12. An apparatus according to  claim 1  further comprising at least one heating source positioned to heat the running fiber bundle. 
     
     
       13. A composite processing machine comprising the apparatus according to  claim 1  positioned downstream from a creel for supplying a running fiber bundle and upstream from an impregnation system. 
     
     
       14. A method for producing a spread fiber bundle comprising:
 a) running a fiber bundle through the apparatus of  claim 1  such that the fiber bundle makes direct wrapping contact with the surface of the series of static bars prior to making direct wrapping contact with the series of driven rollers; and 
 b) controlling tension of the fiber bundle through the apparatus by operating the driven rollers at a peripheral surface speed that is at least three times the speed of the running fiber bundle, thereby spreading the fiber bundle. 
 
     
     
       15. A method according to  claim 14  further comprising heating at least one of the following: the static bars, the driven rollers, and the fiber bundle. 
     
     
       16. A method according to  claim 14  further comprising taking-up the spread fiber with a take-up drum.